Session management method based on reallocation of PDU session anchor device, and device performing the session management method

ABSTRACT

Disclosed is a session management method based on protocol data unit (PDU) session anchor (PSA) relocation, and an device performing the session management method. The session management method may include determining to perform PSA relocation, establishing a new additional PSA device through the PSA relocation, and releasing an existing additional PSA device, in which the PSA relocation may allow traffic moving towards the existing additional PSA device to move to the new additional PSA device.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the priority benefit of Korean PatentApplication No. 10-2017-0035604 filed on Mar. 21, 2017, Korean PatentApplication No. 10-2017-0103670 filed on Aug. 16, 2017, and KoreanPatent Application No. 10-2017-0167798 filed on Dec. 7, 2017, in theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

One or more example embodiments relate to a session management methodbased on a relocation of a protocol data unit (PDU) session anchor (PSA)device, and an device performing the session management method.

2. Description of Related Art

Mobile edge computing (MEC) technology is proposed to provide userequipment (UE) with a low-latency data service. The MEC technology isused to minimize a round-trip time (RTT) between the UE and a serverproviding a service requested by the UE. The MEC technology relates toreducing the number of routing hops between the UE and the server, andalso positioning a geopolitical position of the server closer to the UE.

A fifth-generation (5G) mobile communications network requires thatvarious services are provided to UE through 5G network technology. Thus,the 5G mobile communications network supports edge computing technologyto provide a service of an enhanced quality compared to an existingestablished network.

SUMMARY

An aspect provides a method and device that, when there is a pluralityof edge clouds in a fifth-generation (5G) core network (CN) system, mayprovide load balancing between the edge clouds by changing an edge cloudor resetting a 5G local gateway to support a lifecycle of a virtualized5G local gateway.

Another aspect also provides a method and device that may provideservice flexible to load and connected or continuous despite a movementor mobility of user equipment (UE) by resetting a 5G local gateway,although new UE, in addition to exiting UE, is connected in a 5G CNsystem.

According to an aspect, there is provided a method to be performed by asession management function (SMF) device in a network, the methodincluding determining to perform protocol data unit (PDU) session anchor(PSA) relocation for a PDU session, establishing a new additional PSAdevice through the PSA relocation, and releasing an existing additionalPSA device. The PSA relocation may allow traffic moving towards theexisting additional PSA device to move to the new additional PSA device.

The SMF device may perform the PSA relocation for Internet Protocolversion 6 (IPv6) multi-homing or an uplink classifier.

The SMF device may perform the PSA relocation in response to an eventbenefiting from the PSA relocation for the IPv6 multi-homing or theuplink classifier or a request from an application function.

The SMF device may transmit a session establishment request to the newadditional PSA device, and provide the new additional PSA device with atunnel identifier (ID) of a branching point to be installed, an uplinkclassifier, and packet detection, enforcement, and reporting rules.

The SMF device may transmit, to a user plane function (UPF) devicecorresponding to a branching point or an uplink classifier, a sessionmodification request in accordance with a new IPv6 prefix allocated tothe new additional PSA device to update an uplink traffic filter.

The session modification request may include an ID of a traffic filterfor which the PSA relocation is needed and a tunnel ID of the newadditional PSA device.

When the UPF device corresponding to the branching point or the uplinkclassifier successfully updates all traffic filters for which the SMFdevice requests modification, the UPF device corresponding to thebranching point or the uplink classifier may acknowledge themodification with a session modification response.

The SMF device may transmit, to the existing additional PSA device, asession release request including a session ID, and the existingadditional PSA device may release tunnel resources and contextsassociated with the PDU session.

When the existing additional PSA device successfully releases the tunnelresources and contexts associated with the PDU session, the existingadditional PSA device may transmit a session release response includingthe session ID to the SMF device.

The network may support a session and service continuity (SSC) modeassociated with the PDU session, and the SSC mode may not change duringa lifetime of the PDU session.

According to another aspect, there is provided an SMF device in anetwork, the SMP device that may determine to perform PSA relocation fora PDU session, establish a new additional PSA device through the PSArelocation, and release an existing additional PSA device. The PSArelocation may allow traffic moving towards the existing additional PSAdevice to move to the new additional PSA device.

The SMF device may perform the PSA relocation for IPv6 multi-homing oran uplink classifier.

The SMF device may perform the PSA relocation in response to an eventbenefiting from the PSA relocation for the IPv6 multi-homing or theuplink classifier or a request from an application function.

The SMF device may transmit a session establishment request to the newadditional PSA device, and provide the new additional PSA device with atunnel ID of a branching point to be installed, an uplink classifier,and packet detection, enforcement, and reporting rules.

The SMF device may transmit, to an UPF device corresponding to abranching point or an uplink classifier, a session modification requestin accordance with a new IPv6 prefix allocated to the new additional PSAdevice to update an uplink traffic filter.

The session modification request may include an ID of a traffic filterfor which the PSA relocation is needed and a tunnel ID of the newadditional PSA device.

When the UPF device corresponding to the branching point or the uplinkclassifier successfully updates all traffic filters for which the SMFdevice requests modification, the UPF device corresponding to thebranching point or the uplink classifier may acknowledge themodification with a session modification response.

The SMF device may transmit, to the existing additional PSA device, asession release request including a session ID, and the existingadditional PSA device may release tunnel resources and contextsassociated with the PDU session.

When the existing additional PSA device successfully releases the tunnelresources and contexts associated with the PDU session, the existingadditional PSA device may transmit a session release response includingthe session ID to the SMF device.

The network may support an SSC mode associated with the PDU session, andthe SSC mode may not change during a lifetime of the PDU session.

Additional aspects of example embodiments will be set forth in part inthe description which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, features, and advantages of the presentdisclosure will become apparent and more readily appreciated from thefollowing description of example embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 is a diagram illustrating a core network (CN) including a userplane function (UPF) device corresponding to an uplink classifieraccording to an example embodiment;

FIG. 2 is a diagram illustrating a CN including an UPF devicecorresponding to a branching point for service continuity according toan example embodiment;

FIG. 3 is a diagram illustrating a CN including an UPF devicecorresponding to a branching point for local access to a same datanetwork (DN) according to an example embodiment;

FIG. 4 is a diagram illustrating a protocol stack for a protocol dataunit (PDU) session according to an example embodiment;

FIG. 5 is a diagram illustrating a process of PDU session anchor (PSA)relocation according to an example embodiment;

FIG. 6 is a diagram illustrating a basic situation of a CN according toan example embodiment;

FIG. 7 is a diagram illustrating a first scenario for load balancingaccording to an example embodiment; and

FIG. 8 is a diagram illustrating a second scenario for load balancingaccording to an example embodiment.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, devices, and/orsystems described herein. However, various changes, modifications, andequivalents of the methods, devices, and/or systems described hereinwill be apparent after an understanding of the disclosure of thisapplication. For example, the sequences of operations described hereinare merely examples, and are not limited to those set forth herein, butmay be changed as will be apparent after an understanding of thedisclosure of this application, with the exception of operationsnecessarily occurring in a certain order. Also, descriptions of featuresthat are known in the art may be omitted for increased clarity andconciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, devices, and/or systems described herein that will be apparentafter an understanding of the disclosure of this application.

Terms such as first, second, A, B, (a), (b), and the like may be usedherein to describe components. Each of these terminologies is not usedto define an essence, order, or sequence of a corresponding componentbut used merely to distinguish the corresponding component from othercomponent(s). For example, a first component may be referred to as asecond component, and similarly the second component may also bereferred to as the first component.

It should be noted that if it is described in the specification that onecomponent is “connected,” “coupled,” or “joined” to another component, athird component may be “connected,” “coupled,” and “joined” between thefirst and second components, although the first component may bedirectly connected, coupled or joined to the second component. Inaddition, it should be noted that if it is described in thespecification that one component is “directly connected” or “directlyjoined” to another component, a third component may not be presenttherebetween. Likewise, expressions, for example, “between” and“immediately between” and “adjacent to” and “immediately adjacent to”may also be construed as described in the foregoing.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the,” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises,” “comprising,”“includes,” and/or “including,” when used herein, specify the presenceof stated features, integers, operations, elements, and/or components,but do not preclude the presence or addition of one or more otherfeatures, integers, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms, including technical and scientificterms, used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure pertains based onan understanding of the present disclosure. Terms, such as those definedin commonly used dictionaries, are to be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand the present disclosure, and are not to be interpreted in anidealized or overly formal sense unless expressly so defined herein.

Hereinafter, some example embodiments will be described in detail withreference to the accompanying drawings. Regarding the reference numeralsassigned to the elements in the drawings, it should be noted that thesame elements will be designated by the same reference numerals,wherever possible, even though they are shown in different drawings.

Terms, definitions, and abbreviations used herein are as follows:

A fifth-generation (5G) access network (AN) includes a next generationradio access network (NG-RAN) or a non-third generation partnershipproject (3GPP) (non-3GPP) connected to a 5G core network (CN).

A 5G CN is connected to a 5G AN.

A protocol data unit (PDU) connectivity service refers to a service thatprovides an exchange of PDUs between user equipment (UE) and a datanetwork (DN).

A PDU session refers to an association between UE and a DN to provide aPDU connectivity service.

A PDU session type refers to a type of PDU session, and includesInternet Protocol version 4 (IPv4), IPv6, Ethernet, and the like.

In addition, a session management function (SMF), an access and mobilitymanagement function (AMF), and a user plane function (UPF) that aredescribed herein are software functions, but may be installed orperformed in a single hardware or each of multiple hardware.

Further, definitions of reference points in a 5G system illustrated inFIGS. 1 through 3 are as follows:

N1 indicates a reference point between UE and an AMF.

N2 indicates a reference point between an (R)AN and an AMF.

N3 indicates a reference point between an (R)AN and an UPF.

N4 indicates a reference point between an SMF and an UPF.

N6 indicates a reference point between an UPF and a DN.

In N6, traffic is forwarded between an UPF device acting as an uplink(UL) classifier (CL) (UL CL) and a local DN.

N9 indicates a reference point between two UPFs.

<Session Management>

A 5G CN supports a PDU connectivity service, for example, a service thatprovides an exchange of PDUs between UE and a DN. The PDU connectivityservice is supported via PDU sessions that are established upon requestfrom the UE.

Subscription information includes multiple DN names and a default DNname. In a case in which a valid DN name is not provided in response toa PDU session establishment request, or a request for establishing a PDUsession, that is transmitted to the 5G CN, the UE may be assigned to thedefault DN name.

Each PDU session supports a single PDU session type. For example, a PDUsession supports an exchange of a single type of PDU session requestedby the UE at the establishment of the PDU session.

In the 5G CN, a PDU session is established upon request from the UE,modified upon request from the UE and the 5G CN, and released uponrequest from the UE and the 5G CN.

<User Plane Management>

User plane management handles a user plane path of PDU sessions. A PDUsession supports a deployment of a single UPF device or multiple UPFdevices for the given PDU session. The number of UPF devices for a PDUsession is not restricted.

For a PDU session of an IPv4 or IPv6 type, a PDU session anchor (PSA)may be an Internet Protocol (IP) anchor point of an IP address/prefixallocated to UE. For an IPv4-type PDU session or an IPv6 multi-homed PDUsession, when an UL CL is used and multiple PSAs are used, a single PSAmay be an IP anchor point for the PDU session. For an IPv6 multi-homedPDU session, there are multiple IP anchor points.

<Single PDU Session with Multiple PSAs>

In order to support selective traffic routing for a DN or to supportsession and service continuity (SSC) mode 3, an SMF device may control adata path of a PDU session so that the PDU session may simultaneouslycorrespond to multiple N6 interfaces. An UPF device may terminate theseN6 interfaces to support PSA functionality. Each PSA supporting a PDUsession supports a different access to a same DN, and corresponds to anUPF device. A PSA assigned to establish a PDU session is associated withan SSC mode of the PDU session. In addition, additional PSAs assigned tothe same PDU session, e.g., for the selective traffic routing to the DNare independent of the SSC mode of the PDU session.

The selective traffic routing to the DN supports, for example,deployments where some selected traffic is forwarded, on an N6interface, to the DN that is close to an AN serving UE.

There are two processing methods or modes used to process a PDU session.

(1) FIG. 1 illustrates an UL CL mode based on UL CL functionality for aPDU session.

(2) FIGS. 2 and 3 illustrate an IPv6 multi-homing mode based on IPv6multi-homing for a PDU session.

<UL CL Mode: A Method of Processing an UL CL for a PDU Session>

As illustrated in FIG. 1, in a PDU session of IPv4 or IPv6, or Ethernet,an SMF device may insert an UL CL in a data path of the PDU session.Herein, the inserting of an UL CL indicates inserting an UPF devicecorresponding to the UL CL in the data path from UE to a DN in a 5G CN.

The UL CL refers to functionality supported by UPF device, and is usedto divert (locally) some traffic matching traffic filters provided bythe SMF device. Such an insertion and removal of an UL CL is determinedor controlled by the SMF device using generic N4 and UPF capabilities.The SMF device includes at least one UPF device supporting the UL CLfunctionality in the data path in the PDU session.

The UE is unaware of traffic diversion by the UL CL, and is not involvedin both the insertion and the removal of the UL CL. In a case of a PDUsession of IP types, the UE associates the PDU session with either asingle IPv4 address or a single IPv6 prefix that is allocated by anetwork.

When the UL CL functionality is inserted in the data path of the PDUsession, there are multiple PSAs for the PDU session. These PSAs providedifferent accesses to a same DN. Referring back to FIG. 1, the UPFdevice is an UPF device supporting the UL CL functionality, and an UPFdevice supporting PSA functionality.

The UL CL provides UL traffic forwarding towards different PSAs, andmerges downlink (DL) traffic to the UE. Herein, the traffic from thedifferent PSAs may be merged on a link towards the UE. The merging ofthe traffic may be based on traffic detection and traffic forwardingrules provided by the SMF device.

The UL CL applies filtering rules, and determines how a packet will berouted. Herein, the filtering rules indicate examining a destination IPaddress or a prefix of UL IP packets that is transmitted by the UE. TheUPF device supporting the UL CL may also be controlled by the SMF deviceto support traffic measurement for charging traffic replication for LIand a bit rate enforcement (per PDU session-aggregate maximum bit rate[AMBR]).

For the PDU session for the UL CL, an UL and DL session-AMBR is definedby the SMF device selected by the UPF device supporting the UL CLfunctionality.

In addition, the UPF device supporting the UL CL may also support a PSAfor connectivity to local access to the DN. For example, the UPF devicemay support tunnelling or network address translation (NAT) on N6. TheUPF device may be controlled by the SMF device.

Additional UL CLs or additional PSAs may be inserted in the data path ofthe PDU session to generate new data paths for the same PDU session. Howto organize a data path of all UL CLs in a PDU session is based on anoperator configuration and SMF logic. In addition, there is only one UPFdevice supporting an UL CL connecting it to an AN through an N3interface.

FIG. 1 illustrates an example of how an UPF device is inserted in a datapath of a PDU session. A same UPF may support both UL CL functionalityand PSA functionality. In an UL CL mode illustrated in FIG. 1, UE maynot be involved in a procedure for service continuity, and an SMF devicemay selectively release an existing additional PSA in the UL CL mode.

<IPv6 Multi-Homing Mode: A Method of Processing an IPv6 Multihome for aPDU Session>

A PDU session may be associated with multiple IPv6 prefixes, which isreferred to as a multi-homed PDU session. The multi-homed PDU sessionprovides access to a DN via one or more PSAs. Herein, different userplane paths leading to different PSAs branch out at a common UPF that isreferred to as an UPF supporting branching point functionality. Herein,a branching point provides UL traffic forwarding towards the differentPSAs, and merges traffic from the different PSAs towards UE on a link.

The UPF device supporting the branching point functionality may also becontrolled by an SMF device to support traffic measurement for chargingtraffic replication for LI and bit rate enforcement per PDU sessionAMBR. The insertion and removal of the UPF device supporting thebranching point may be determined or controlled by the SMF device usinggeneric N4 and UPF capabilities. The SMF device may decide to insert theUPF device supporting the branching point functionality in a data pathof a PDU session during or after establishment of the PDU session.Alternatively, the SMF device may decide to remove the UPF devicesupporting the branching point functionality from the data path of thePDU session after the establishment of the PDU session.

The multi-homing of the PDU session may be applied to PDU sessions ofIPv6 type. A request of a PDU session type “IP” or “IPv6” impliessupporting a multi-homed PDU session for IPv6 in the UE.

Using multiple IPv6 prefixes in a PDU session may have the followingcharacteristics.

The UPF device supporting the branching point functionality isconfigured by the SMF device to spread UL traffic between IP anchorsbased on a source prefix of a PDU. The source prefix may be selected bythe UE based on routing information and preferences received from anetwork.

The Internet Engineering Task Force (IETF) Request for Comments (RFC)4191 is used to configure the routing information and the preferencesinto the UE to influence the selection of the source prefix. Thiscorresponds to “IPv6 multi-homing without network address translation(NAT),” scenario 1 defined in the IETF RFC. This allows the branchingpoint to be generated without being aware of routing table in a DN, anda first hop router function to be kept in the IP anchors.

As illustrated in FIG. 2, a multi-homed PDU session may be used tosupport make-before-break service continuity to support SSC mode 3.

In addition, as illustrated in FIG. 3, a multi-homed PDU session mayalso be used to support cases where UE needs to access both a localservice (e.g., a local server) and a central service (e.g., Internet).

The UE may use a method associated with “Relocation of SSC mode 3 PSAwith IPv6 multi-homed PDU session,” to determine whether the multi-homedPDU session is used to support service continuity or it is used tosupport local access to a DN.

According to an example embodiment, an UPF device may support bothbranching point functionality and PSA functionality.

<Session and Service Continuity (SSC)>

Supporting SSC in 5G system architecture enables to address variouscontinuity requirements of different applications and services for UE. A5G system supports different SSC modes. An SSC mode associated with aPDU session does not change during a lifetime of the PDU session.

With SSC mode 1, a network may preserve a connectivity or continuityservice provided to the UE. For a case of a PDU session of an IPv4 orIPv6 type, an IP address is preserved.

With SSC mode 2, the network may release a connectivity or continuityservice delivered to the UE and a PDU session corresponding to theconnectivity or continuity service. For a case of an IPv4 or IPv6 type,the network may release IP addresses that had been allocated to the UE.

With SSC mode 3, changes to a user plane may be visible to the UE, whilethe network may ensure that the UE suffers no loss of connectivity. Aconnection through a new additional PSA is established before a previousconnection is terminated in order to allow for better servicecontinuity. For a case of an IPv4 or IPv6 type, an IP address is notpreserved in this mode when the PSA changes.

The addition or removal procedure of an additional PSA in a PDU sessionfor local access to a DN is independent from an SSC mode of the PDUsession.

<SSC Mode>

(1) SSC Mode 1

For a PDU session of SSC mode 1, an UPF acting as a PSA at theestablishment of the PDU session is maintained regardless of accesstechnique, for example, an access type and cells, which is for UE tosuccessfully access a network.

In a case of a PDU session of an IPv4 or IPv6 type, IP continuity issupported regardless of UE mobility events.

When an IPv6 multi-homing or an UL CL applies to the PDU session of SSCmode 1, the network allocates additional PSAs to the PDU session basedon local policies. These additional PSAs may be released or allocated,and the UE does not expect that an additional IPv6 prefix is maintainedduring a lifetime of the PDU session. SSC mode 1 may apply to any PDUsession types or any access types.

(2) SSC Mode 2

In a case in which a PDU session of SSC mode 2 has a single PSA, thenetwork may trigger a release of the PDU session and instruct the UE toestablish a new PDU session to a same DN immediately. A triggercondition depends on an operator policy, for example, a request from anapplication function based on a load status and the like. At theestablishment of the new PDU session, a new UPF acting as a PSA may beselected.

Otherwise, in a case in which the PDU session of SSC mode 2 has multiplePSAs, for example, in a case in which a multi-homed PDU session or an ULCL applies to the PDU session of SSC mode 2, additional PSAs may bereleased or allocated.

SSC mode 2 may apply to any PDU session types and access types. In an ULCL mode, the UE is not involved in PSA reallocation so that theexistence of multiple PSAs is not visible to the UE.

(3) SSC Mode 3

For a PDU session of SSC mode 3, the network allows the establishment ofUE connectivity to a same DN via a new additional PSA beforeconnectivity between the UE and a previous PSA is released. With triggerconditions applied, the network decides whether to select an UPFsupporting a PSA suitable for UE's new conditions, for example, a pointof attachment to the network.

SSC mode 3 may apply to any PDU session types and any access types.

In a case of a PDU session of an IPv4 or IPv6 type, a procedure ofchanging a PSA is performed. A new IP prefix anchored on a newadditional PSA may be allocated within the same PDU session (relying onIPv6 multi-homing). Alternatively, the new IP prefix may apply to a caseof a PDU session setup in SSC mode 3 or additional PSAs of the PDUsession established in SSC mode 1. The new IP address or the new IPprefix may be allocated within a new PDU session for which theestablishment is triggered by the UE.

After the new IP address or the new IP prefix has been allocated, theold IP address or prefix is maintained during some time indicated to theUE and then released.

In a case in which the PDU session of SSC mode 3 has multiple PSAs, forexample, in a case of a multi-homed PDU session or in case an UL CLapplies to the PDU session of SSC mode 3, additional PSAs may bereleased or allocated.

<SSC Mode Selection>

An SSC mode selection policy may be used to determine a session type ora type of SSC mode associated with an application or group ofapplications for UE.

It is possible for an operator to provide the UE with the SSC modeselection policy. The SSC mode selection policy includes one or more SSCmode selection policy rules that may be used by the UE to determine atype of SSC mode associated with an application or group ofapplications. The SSC mode selection policy may also include a defaultSSC mode selection policy rule that matches all applications of the UE.

When an application requests data transmission, for example, opening anetwork socket, and the application itself does not specify a requiredSSC mode, the UE determines an SSC mode associated with this applicationby using the SSC mode selection policy. In addition, the followingbehavior applies for the UE and network.

a) In a case in which the UE has an already established PDU session thatmatches the SSC mode associated with the application, the UE routes dataof the application within this PDU session unless other conditions inthe UE do not permit the use of this PDU session. Otherwise, the UErequests the establishment of a new PDU session that matches the SSCmode associated with the application.

b) The SSC mode associated with the application is either an SSC modeincluded in a non-default SSC mode selection policy rule that matchesthe application, or an SSC mode included in the default SSC modeselection policy rule, if present. In a case in which the SSC modeselection policy does not include a default mode selection policy ruleand no other rule matches the application, the UE requests a PDU sessionwithout providing the SSC mode. In this case, the network determines theSSC mode of the PDU session.

The SSC mode selection policy rule provided to the UE may be updated bythe operator.

An SW′ device receives, from a unified data management (UDM) device, alist of supported SSC modes and the default SSC mode per data networkname (DDN) as part of subscription information.

In a case in which the UE provides an SSC mode when requesting a new PDUsession, the SMF device selects the SSC mode by either accepting therequested SSC mode or modifying the requested SSC mode based onsubscription or local configuration.

In a case in which the UE does not provide an SSC mode when requesting anew PDU session, the SMF device selects a default SSC mode for a DN thatis listed in the subscription or applies local configuration to selectthe SSC mode.

In a case in which a static IP address/prefix is allocated to a PDUsession, SSC mode 1 may be assigned to the PDU session based on thestatic IP address/prefix subscription for the DNN and single networkslice selection assistance information (S-NSSAI).

FIG. 4 is a diagram illustrating a protocol stack for a PDU sessionaccording to an example embodiment.

FIG. 4 illustrates a protocol stack for a user plane transportassociated with a PDU session.

PDU layer: This layer corresponds to a PDU carried between UE and a DNover a PDU session. In a case of a PDU session type being IPv6, the PDUlayer corresponds to IPv6 packets. In a case of a PDU session type beingEthernet, the PDU layer corresponds to Ethernet frames.

General packet radio service (GPRS) tunneling protocol for a user plane(GTP-U): This GTP-U protocol supports multiplexing traffic of differentPDU sessions (possibly corresponding to different PDU session types) bytunneling user data over N3, for example, an interface between a 5G ANnode and an UPF device, in a backbone network.

The GTP may encapsulate PDUs, and provide encapsulation on a per PDUsession level and also carry marking associated with a quality ofservice (QoS) flow.

5G encapsulation: A 5G encapsulation layer supports multiplexing trafficof different PDU sessions (possibly corresponding to different PDUsession types) over N9, for example, an interface between different UPFsin a 5G CN. The 5G encapsulation provides encapsulation on a per PDUsession level. The 5G encapsulation layer may also carry markingassociated with a QoS flow.

5G AN protocol stack: This stack is a set of protocols and layersdependent on an AN.

The number of UPF devices in a data path is not restricted. In a case inwhich there is an UL CL or a branching point in a data path of a PDUsession, the UL CL or the branching point acts as an UPF devicecorresponding to non-PSA. In that case, there are multiple N9 interfacesbranching out of the UL CL or the branching point each leading todifferent PSAs.

FIG. 5 is a diagram illustrating a process of PSA relocation accordingto an example embodiment.

A process of PSA relocation illustrated in FIG. 5 may be triggered by anSMF device. A process of additional PSA relocation described withreference to FIG. 5 may be independent of an SSC mode of a PDU session.

Herein, when the SMF device needs to modify an IPv6 multi-homing or ULCL rule, the SMF device performs the PSA relocation. The IPv6multi-homing or UL CL rule may be a traffic filter in IPv6 multi-homingor an UL CL.

When there is a need to modify the IPv6 multi-homing or UL CL rule, anadditional PSA is established by the IPv6 multi-homing or the UL CL andsome or whole traffic moves to the additional PSA. In FIG. 5, PSA1 andPSA2 indicate additional PSAs. In detail, PSA1 indicates an existingadditional PSA, and PSA2 indicates a new additional PSA. Both PSA1 andPSA2 are established by a same branching point or UL CL.

Hereinafter, the branching point or the UL CL may indicate an UPF devicecorresponding to the branching point or the UL CL.

Step 1

The SMF device determines to perform additional PSA relocation due toevents that may benefit from PSA relocation for IPv6 multi-homing or ULCL, or due to a request from an application function via the SMF device.

Step 2

The SMF device transmits an N4 session establishment request to PSA2 andprovides PSA2 with a tunnel identifier (ID) of a branching point or anUL CL to be installed, and packet detection, enforcement, and reportingrules. When a tunnel ID is allocated by the SMF, the tunnel ID isprovided to PSA2 in this step. PSA2 acknowledges this by transmitting anN4 session establishment response. The tunnel ID of PSA2 is provided tothe SMF device in this step.

In a case of an IPv6 multi-homing PDU session, the SMF device allocatesa new IPv6 prefix corresponding to PSA2.

Step 3a

The SMF device transmits an N4 session modification request to thebranching point or the UL CL to update an UL traffic filter according tothe new IPv6 prefix allocated to PSA2 or an UL CL rule regarding atraffic flow that the SMF device tries to move from PSA1 to PSA2. The N4session modification request includes IDs of traffic filters that needthe PSA relocation and the tunnel ID of PSA2 so that the branching pointor the UL CL updates PSA2 to an N9 interface for the traffic filtersthat need the PSA relocation.

An ID of a traffic filter may be one of an index of the traffic filter,a single value of an information field in the traffic filter (e.g., atunnel ID of a next hop), and a combination value of some informationfield in the traffic filter (e.g., a tunnel ID of a next hop with asource port number).

Step 3b

When the branching point or the UL CL successfully updates all thetraffic filters that the SMF requests the modification, the branchingpoint or the UL CL acknowledges the modification with an N4 sessionmodification response.

Step 4

In a case of the IPv6 multi-homing PDU session, the SMF device notifiesUE of availability of the new IP prefix at PSA2. This is performed usingan IPv6 router advertisement message. Also, the SMF device transmits arouting rule along with the IPv6 prefix to the UE using the IPv6 routeradvertisement message. In a case of an UL CL PDU session, step 4 may beomitted.

Step 5

In a case of the IPv6 multi-homing PDU session, the SMF devicereconfigures the UE for the original IP prefix at PSA0. For example, theSMF device transmits a routing rule along with the IPv6 prefix to the UEusing the IPv6 router advertisement message.

Step 6

This step occurs only if the branching point or the UL CL does not haveany traffic filter on the PDU session that forwards a traffic flow toPSA1. The SMF device selectively releases an existing additional PSA.

Step 6a

The SMF device transmits an N4 session release request with an N4session ID to PSA1. PSA1 releases all tunnel resources and contextsassociated with the N4 session.

Step 6b

When PSA1 successfully release all the tunnel resources and contextsassociated with the N4 session, PSA1 transmits an N4 session releaseresponse with the N4 session ID to the SMF device.

FIGS. 6 through 8 are diagrams illustrating examples of load balancingthrough edge computing.

An edge cloud and a central cloud for the edge computing may correspondto a DN described with reference to FIGS. 1 through 5. In detail, theedge cloud corresponds to a local DN, and the central cloud correspondsto a common DN such as the Internet.

Referring to FIG. 6, UE receives a service from the edge cloud and thecentral cloud through a 5G CN.

The operations of each of components or elements illustrated in FIGS. 6through 8 are described as follows.

1) Uplink classifier (UL CL): An UP CL is a virtualized UPF and presentbetween an RAN and a 5G gateway, and is configured to transmit ULtraffic of the UE to a predetermined gateway based on a set rule andsynthesize DL traffic received through different gateways to transmit itto the UE.

2) User plane function (UPF) 0 (PSA0): PSA0 acts as a gateway of the 5Gnetwork to connect the UE and the central cloud, and has an IP addressfor a corresponding session.

3) UPF (PSA1): PSA1 acts as a gateway of the 5G network to connect theUE to edge cloud 1, and has an IP address such as UPF0 for acorresponding session.

4) Edge cloud or edge cloud 1: As an external 5G DN having a same DNN asthat of the central cloud, and the edge cloud provides some of servicesof the central cloud or locally specified service.

5) Session management function (SMF) device: As a function of managing asession of the UE in the 5G CN, the SMF connects the UE to the centralcloud and the edge cloud by controlling UPFs through the SMF.

Referring to FIG. 7, new gateway UPF2 is set to connect to a new edgecloud, or edge cloud 2, in a 5G CN in order to distribute loadconcentrated on a central cloud or edge cloud 1.

Referring to FIG. 8, in a case in which a gateway is generated (e.g.,UPF (PSA2)) and released (e.g., UPF (PSA1)) due to load balancing or alifecycle of a virtualized 5G gateway (UPF), a service that is providedonce through UPF(PSA1) is provided through UPF(PSA2) as UPF(PSA1) isreplaced with UPF(PSA2).

The processes described above are as follows.

(i) An SMF device determines that there is a need to connect a new localgateway, UPF(PSA2), for a corresponding PDU session, based on a load ofa central cloud and edge cloud 1, or on a lifecycle of UPF(PSA1). Thatis, the SMF device determines whether there is a need for PSArelocation.

(ii) The SMF device selects a 5G gateway, UPF(PSA2), to connect a newlocal gateway, and sets a tunnel ID of the UPF device.

(iii) The SMF device requests an UL CL to set a rule to select trafficto be transmitted to the newly set UPE(PSA2) for edge cloud 2 or 1. Therule may be set based on an index of a previous rule or a tunnel ID of anext hope, or a single value of a port number or a combination of eachvalue.

(iv) When all traffic is moved to UPF(PSA0) or UPF(PSA2) through (iii),for example, scenario 2, the SMF device releases UPF(PSA1). However,when the UE still receives a service from edge cloud 1 through UPF(PSA1)even after (iii), the SMF device does not perform (iv) and not releaseUPF(PSA1).

According to example embodiments described herein, load balancingbetween UPFs in an edge cloud or a 5G CN may be enabled, and a qualityof an edge service through the 5G CN may also be enhanced.

In addition, through a 5G edge computing signaling method that isadaptive to network dynamics, such as, a change in lifecycle of avirtualized UPF (e.g., generation, scaling up and down, and release ordisappearance of the UPF), virtualization of the 5G CN providing an edgeservice may be supported.

The methods described herein may be configured as programs implementablein a computer, and embodied through various recording media, such as,for example, a magnetic storage medium, an optical read medium, adigital storage medium, and the like.

According to example embodiments described herein, when there is aplurality of edge clouds in a 5G CN system, load balancing between theedge clouds may be enabled by changing an edge cloud or resetting a 5Glocal gateway to support a lifecycle of a virtualized 5G local gateway.

According to example embodiments described herein, although new UE, inaddition to existing UE, is connected in a 5G CN system, a service thatis flexible to a load and connected or continuous despite a movement ofUE may be provided by resetting a 5G local gateway.

The components described in the example embodiments of the presentdisclosure may be achieved by hardware components including at least oneof a digital signal processor (DSP), a processor, a controller, anapplication specific integrated circuit (ASIC), a programmable logicelement such as a field programmable gate array (FPGA), other electronicdevices, and combinations thereof. At least some of the functions or theprocesses described in the example embodiments of the present disclosuremay be achieved by software, and the software may be recorded on arecording medium. The components, the functions, and the processesdescribed in the example embodiments of the present disclosure may beachieved by a combination of hardware and software.

The processing device described herein may be implemented using hardwarecomponents, software components, and/or a combination thereof. Forexample, the processing device and the component described herein may beimplemented using one or more general-purpose or special purposecomputers, such as, for example, a processor, a controller and anarithmetic logic unit (ALU), a digital signal processor, amicrocomputer, a field programmable gate array (FPGA), a programmablelogic unit (PLU), a microprocessor, or any other device capable ofresponding to and executing instructions in a defined manner. Theprocessing device may run an operating system (OS) and one or moresoftware applications that run on the OS. The processing device also mayaccess, store, manipulate, process, and create data in response toexecution of the software. For purpose of simplicity, the description ofa processing device is used as singular; however, one skilled in the artwill be appreciated that a processing device may include multipleprocessing elements and/or multiple types of processing elements. Forexample, a processing device may include multiple processors or aprocessor and a controller. In addition, different processingconfigurations are possible, such as parallel processors.

The methods according to the above-described example embodiments may berecorded in non-transitory computer-readable media including programinstructions to implement various operations of the above-describedexample embodiments. The media may also include, alone or in combinationwith the program instructions, data files, data structures, and thelike. The program instructions recorded on the media may be thosespecially designed and constructed for the purposes of exampleembodiments, or they may be of the kind well-known and available tothose having skill in the computer software arts. Examples ofnon-transitory computer-readable media include magnetic media such ashard disks, floppy disks, and magnetic tape; optical media such asCD-ROM discs, DVDs, and/or Blue-ray discs; magneto-optical media such asoptical discs; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory (e.g., USB flash drives, memorycards, memory sticks, etc.), and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter. The above-described devices may beconfigured to act as one or more software modules in order to performthe operations of the above-described example embodiments, or viceversa.

A number of example embodiments have been described above. Nevertheless,it should be understood that various modifications may be made to theseexample embodiments. For example, suitable results may be achieved ifthe described techniques are performed in a different order and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Accordingly, other implementations arewithin the scope of the following claims.

What is claimed is:
 1. A method to be performed by a session managementfunction (SMF) device in a network, the method comprising: determiningto perform protocol data unit (PDU) session anchor (PSA) relocation fora PDU session; performing the PDU session anchor relocation, wherein theperforming the PDU session anchor relocation comprising: determining, bythe SMF device, PDU session anchor relocation according to event or arequest from an application function; transmitting session establishmentrequest to a new PSA device and providing a tunnel ID of UL(Uplink)CL(Classifier), when the tunnel ID is allocated by the SMF device, thetunnel ID is provided to the new PSA device; transmitting a sessionmodification request to the UL CL to update an UL traffic filteraccording to an UL CL rules regarding a traffic flow that the SMF devicetries to move from an existing PSA device to the new PSA device, whereinthe session modification request includes identification of the ULtraffic filter; and receiving a session modification response, when theUL CL successfully updates all the UL traffic filters that the SMFdevice requests to modify.
 2. The method of claim 1, further comprising:transmitting a session release request with a session ID to the existingPSA device, wherein the existing PSA device release all tunnel resourcesand contexts associated with a session; receiving a session releaseresponse with a session ID from the existing PSA device, when theexisting PSA device release successfully releases all tunnel resourcesand contexts associated with the session.
 3. The method of claim 1,wherein the SMF device is configured to perform the PSA relocation inresponse to an event benefiting from the PSA relocation for the IPv6multihoming or the uplink classifier or a request from an applicationfunction.
 4. The method of claim 1, wherein the SMF device is configuredto transmit a session establishment request to the new PSA device, andprovide the new PSA device with a tunnel identifier (ID) of a branchingpoint to be installed, an uplink classifier, and packet detection,enforcement, and reporting rules.
 5. The method of claim 1, wherein theSMF device is configured to transmit, to a user plane function (UPF)device corresponding to a branching point or an uplink classifier, asession modification request in accordance with a new IPv6 prefixallocated to the new PSA device to update the UL traffic filter.
 6. Themethod of claim 5, wherein the session modification request includes anID of the UL traffic filter for which the PSA relocation is needed and atunnel ID of the new PSA device.
 7. The method of claim 5, wherein, whenthe UPF device corresponding to the branching point or the uplinkclassifier successfully updates all the UL traffic filters for which theSMF device requests modification, the UPF device corresponding to thebranching point or the uplink classifier is configured to acknowledgethe modification with a session modification response.
 8. The method ofclaim 1, wherein the SMF device is configured to transmit, to theexisting PSA device, a session release request including a session ID,and the existing PSA device is configured to release tunnel resourcesand contexts associated with the PDU session.
 9. The method of claim 8,wherein, when the existing PSA device successfully releases the tunnelresources and contexts associated with the PDU session, the existing PSAdevice is configured to transmit a session release response includingthe session ID to the SMF device.
 10. The method of claim 1, wherein thenetwork is configured to support a session and service continuity (SSC)mode associated with the PDU session, wherein the SSC mode does notchange during a lifetime of the PDU session.
 11. A session managementfunction (SMF) device in a network, the SMF device configured to:determine to perform protocol data unit (PDU) session anchor (PSA)relocation for a PDU session; perform the PDU session anchor relocation;wherein the PDU session anchor relocation is performed according tobelow steps including: determine, by the SMF device, PDU session anchorrelocation according to event or a request from an application function;transmit session establishment request to a new PSA device and providinga tunnel ID of UL(Uplink) CL(Classifier), when the tunnel ID isallocated by the SMF device, the tunnel ID is provided to the new PSAdevice; transmit a session modification request to the UL CL to updatean UL traffic filter according to an UL CL rules regarding a trafficflow that the SMF device tries to move from an existing PSA device tothe new PSA device, wherein the session modification request includesidentification of the UL traffic filter; and receive a sessionmodification response, when the UL CL successfully updates all the ULtraffic filters that the SMF device requests to modify.
 12. The SMFdevice of claim 11, further configured to: transmit a session releaserequest with a session ID to the existing PSA device, wherein theexisting PSA device release all tunnel resources and contexts associatedwith a session; receive a session release response with a session IDfrom the existing PSA device, when the existing PSA device releasesuccessfully releases all tunnel resources and contexts associated withthe session.
 13. The SMF device of claim 11, configured to perform thePSA relocation in response to an event benefiting from the PSArelocation for the IPv6 multihoming or the uplink classifier or arequest from an application function.
 14. The SMF device of claim 11,configured to transmit a session establishment request to the new PSAdevice, and provide the new PSA device with a tunnel identifier (ID) ofa branching point to be installed, an uplink classifier, and packetdetection, enforcement, and reporting rules.
 15. The SMF device of claim11, configured to transmit, to a user plane function (UPF) devicecorresponding to a branching point or an uplink classifier, a sessionmodification request in accordance with a new IPv6 prefix allocated tothe new PSA device to update the UL traffic filter.
 16. The SMF deviceof claim 15, wherein the session modification request includes an ID ofthe UL traffic filter for which the PSA relocation is needed and atunnel ID of the new PSA device.
 17. The SMF device of claim 15,wherein, when the UPF device corresponding to the branching point or theuplink classifier successfully updates all the UL traffic filters forwhich the SMF device requests modification, the UPF device correspondingto the branching point or the uplink classifier is configured toacknowledge the modification with a session modification response. 18.The SMF device of claim 11, configured to transmit, to the existing PSAdevice, a session release request including a session ID, wherein theexisting PSA device is configured to release tunnel resources andcontexts associated with the PDU session.
 19. The SMF device of claim18, wherein, when the existing PSA device successfully releases thetunnel resources and contexts associated with the PDU session, theexisting PSA device is configured to transmit a session release responseincluding the session ID to the SMF device.
 20. The SMF device of claim11, wherein the network is configured to support a session and servicecontinuity (SSC) mode associated with the PDU session, wherein the SSCmode does not change during a lifetime of the PDU session.